For example, as disclosed in PTL 1, a lock device for locking a linear motion rod of a hydraulic cylinder is conventionally and widely known that fixes a lock device body, through which a rod penetrates, to a rod exit of the hydraulic cylinder and that is provided, inside of the lock device body, with a brake member that fastens the rod. The brake member has a thick walled cylindrical shape with an inner diameter that is smaller than an outer diameter of the rod and includes an opening portion that is slit in an axis direction in a portion of the cylinder and a pair of pressure-bearing sections opposite each other on both sides of the opening portion. By pushing and opening the pair of pressure-bearing sections by driving a lock release piston provided inside the lock device body, the fastening of the rod with the brake member is released so as to unlock the lock, and when locking the rod, the piston is returned to fasten the rod by the elastic force of the brake member itself such that the rod is locked.
Describing in further detail, in the lock device, a taper-shaped expansion portion is inserted between a pair of pressure-bearing sections of the brake member through rollers. By providing the taper-shaped expansion portion in the lock release piston and by supplying and discharging a pressure fluid from the outside to a piston chamber defined inside the lock device body, the piston is driven. That is, the taper-shaped expansion portion is disposed such that by driving the piston with the pressure fluid supplied to the piston chamber, the taper-shaped expansion portion can be pushed in between the pair of rollers that abut the pressure-bearing section of the brake member. By pushing in the taper-shaped expansion portion, the pressure-bearing section is expanded such that the rod is unlocked. Upon discharge of the pressure fluid from the piston chamber, the piston is returned with biasing force of the return spring acting on the piston and with the elastic force of the brake member itself, the peripheral surface of the rod is fastened such that the rod is locked.
Such a lock device described above is expected to be capable of being unlocked and locked with the lock release piston while that unlocking and locking of the rod can be performed by manual operation. Furthermore, there is a lock device such as the lock device described above that is supplied to the market as a product with a configuration that enable locking and unlocking to be performed with a manual operation bolt 60 illustrated in FIG. 6.
Referring to FIGS. 6 and 7, a configuration of a known lock device will be described. A lock release piston 43 is housed in a piston chamber 42 formed inside a lock device body 41, and a supply and discharge port 44 of a pressure fluid that is in communication with the piston chamber 42 is established in the lock device body 41. A pressure projection 45 for pressing the piston 43 in the lock release direction from the outside is integrally formed with the piston 43, and the pressure projection 45 is fitted into a screw hole 46 for screwing a manual operation bolt 60 formed separately with respect to the lock device body 41. Furthermore, the lock device is configured such that lock of a rod 40 of the brake member 50 can be released manually by screwing the manual operation bolt 60 into the screw hole 46 such that the manual operation bolt 60 presses an operation end of the pressure projection 45 and pushes a taper-shaped expansion portion 43b in between a pair of pressure-bearing section 51 of a brake member 50 so as to push and open the pressure-bearing section 51. Note that in FIGS. 6 and 7, a state in which the manual operation bolt 60 is detached from the screw hole 46 and in which a dust-proof cover 61 is screwed to the screw hole 46 is illustrated.
As described above, when a measure is taken in which the pressure projection 45 for manual operation is integrally provided with the lock release piston 43 and in which the pressure projection 45 is pressed with the manual operation bolt 60 formed as a dedicated member for unlocking, the manual operation bolt 60 and the dust-proof cover 61 that closes the screw hole 46 need to be prepared separately, and when not in use, they need to be stored at a different place.
Furthermore, in order to prevent the pressure liquid that is introduced into the piston chamber 42 from the supply and discharge port 44 from leaking, a portion between an inner peripheral surface of the screw hole 46 and an outer peripheral surface of the pressure projection 45 needs to be sealed with a sealing ring 47. In such a case, the sealing ring 47 needs to be attached to a portion inside the screw hole 46 that is different from where the female screw is threaded. Furthermore, the sealing of the sealing ring 47 needs to be performed in the entire range of the stroke length of the piston 43, and the screw hole 46 needs to be formed with a surplus in the axial direction so as to allow the manual operation bolt 60 to be screwed in even when the pressure projection 45 is positioned at an up end. As a result, not only the structure of the device becomes complicated, the screw hole 46 becomes relatively long, and there is a problem in that the length of the lock device body 41 in the up-down direction tends to become large accordingly.